In the control of fluid in industrial processes, such as oil and gas pipeline systems, chemical processes, etc., it is often necessary to reduce and control the pressure of a fluid. Regulators are typically used for these tasks by providing adjustable flow restriction through the regulator. The purpose of the regulator in a given application may be to control pressure, flow rate, or other process variables, but the restriction inherently induces a pressure reduction as a by-product of its flow control function.
By way of example, a specific application in which regulators are used is the distribution and transmission of natural gas. A natural gas distribution system typically includes a piping network extending from a natural gas field to one or more consumers. In order to transfer large volumes of gas, the gas is compressed to an elevated pressure. As the gas nears the distribution grid and, ultimately, the consumers, the pressure of the gas is reduced at pressure reducing stations. The pressure reducing stations often use regulators to reduce gas pressure.
Some of such pressure reducing stations may be located at or near a custody transfer point in the distribution system. For example, pressure reducing stations that use regulators to reduce gas pressure may be located at a location of a consumer, such as a residential, commercial, or industrial end user.
Accuracy of flow measurement may be important at such custody transfer points, and flow measurement is typically carried out by the use of one or more flow meters. However, flow meters can be expensive to build, install, and maintain, and other means for providing accurate flow measurement without the added expense of flow meters would be beneficial. Flow measurement problems similar to those described above with respect to natural gas distribution are also present in other regulator applications (i.e., industrial processes, chemical processes, etc., including applications that involve steam and other types of liquids and/or gases).